Oxidative dehydrogenation of ethane using carbon dioxide

ABSTRACT

The present disclosure relates to methods and systems suitable for chemical production by dehydrogenation of ethane utilizing carbon dioxide as a soft oxidant. Ethane and carbon dioxide are reacted in a catalytic reactor to produce a reaction product stream comprising at least ethylene and carbon dioxide. The carbon dioxide can be separated for recycling back into the catalytic reactor, and the ethylene can be upgraded using a variety of process units. Heat from the reaction product stream can be recycle for further uses, including reducing the amount of added heating needed in the catalytic reactor. Additional materials, such carbon monoxide, hydrogen, syngas, methanol, methane, ethane, and even heavier hydrocarbons can be provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 16/113,722, filed Aug. 27, 2018, which claims priority to U.S.Provisional Patent Application No. 62/550,990, filed Aug. 28, 2017, thedisclosures of which are incorporated herein by reference in theirentireties.

FIELD OF THE DISCLOSURE

The present disclosure provides chemical production processes. Inparticular, the present disclosure relates to chemical conversionprocesses utilizing CO₂ as an oxidant.

BACKGROUND

Many chemical conversion processes are very energy intensive and canalso be the source of various pollutants. For example, known methods forgenerating ethylene include steam cracking of ethane or naptha, and suchprocesses are known to consume as much as 1% of the world's energyproduction. The process also results in significant carbon dioxideemissions. In addition, carbon coking (via the Boudouard reaction) ofthe catalysts used in the cracking processes can result in thedeactivation of the catalyst, which can further drive up the cost of theprocess. Accordingly, there remains a need in the art for furtherchemical conversion processes.

SUMMARY OF THE DISCLOSURE

The present disclosure relates to chemical production processesutilizing ethane (C₂H₆) as a starting material. For example, the presentdisclosure can provide for the production of ethylene (C₂H₄) utilizingethane as a starting material. The present processes can reduce theenergy requirement for the chemical production, can prevent catalystdeactivation, can consume (instead of producing) carbon dioxide (CO₂),and can generate other valuable commodity materials, such as hydrogengas (e.g., via a water gas shift reaction) and/or methanol (e.g., viareverse water gas shift followed by methanol synthesis).

In one or more embodiments, the presently disclosed methods can utilizecarbon dioxide as a soft oxidant to perform oxidative dehydrogenation(ODH) of ethane and thus achieve ethylene production through ethane CO₂cracking. The methods can include providing ethane and carbon dioxideinto a suitable reactor and utilizing heat supplied from a suitablethermal source (e.g., concentrated solar energy, combustion, geothermal,or industrial sources). One or both of the ethane and the carbon dioxidecan be heated prior to passage into the reactor, such as by passagethrough a heat exchanger, which may utilize waste heat recuperated froma further stage of the conversion method. Oxidative dehydrogenation(ODH) of ethane in the reactor can yield a number of products includingethylene, unconverted ethane, carbon dioxide, carbon monoxide (CO),hydrogen (H₂), methane (CH₄), water (H₂O), and possibly trace amounts ofheavier hydrocarbons depending upon the catalyst used and the overallreaction conditions.

Beneficially, the reaction conditions can be optimized to drive thereaction to a desired ratio of reaction products. For example, in someembodiments, ethylene, carbon monoxide, and water can be present as theprimary reaction products. In such embodiments, various separationtechniques and conversion techniques can be applied to the reactionproducts to isolate ethylene and to utilize the remaining reactionproducts in formation of even further materials, such as methanol. Inpreferred embodiments, the ODH reaction can be carried out so that thereaction products include a larger number of reaction products. Asfurther described herein, the more complex reaction product mixture canthen be further processed to isolate desired commodities, recuperateheat, and recycle chemicals for further reaction.

In one or more embodiments, the present disclosure specifically canprovide methods for chemical production from ethane. In exampleembodiments, such methods can comprise: providing ethane and carbondioxide into a reactor at a molar ratio so that the amount of providedcarbon dioxide is in excess of the stoichiometrically required amountfor complete reaction with the ethane; reacting the ethane with thecarbon dioxide in a reactor in the presence of a catalyst to form areaction product stream at a temperature of about 450° C. or greatercomprising at least ethylene and carbon dioxide; passing the reactionproduct stream through a primary heat exchanger to withdraw heattherefrom; removing water and optionally any further condensates presentin the reaction product stream; compressing the reaction product streamto a pressure of at least 20 bar; separating carbon dioxide from thereaction product stream in a separation unit to provide an upgradedethylene stream; heating at least a portion of the carbon dioxideseparated from the reaction product stream using the heat withdrawn fromthe reaction product stream to form a stream of heated carbon dioxide;recycling the stream of heated carbon dioxide back into the reactor; andfurther processing the upgraded ethylene stream to provide at leastethylene as a produced chemical. In further embodiments, the methods canbe characterized by one or more of the following statements, which canbe combined in any order or number.

The reactor can be a fixed bed reactor catalytic reactor or a fluidizedbed catalytic reactor.

The reaction product stream can be at a temperature of about 500° C. toabout 800° C.

The reaction product stream can comprise at least 10% by mass carbondioxide based on the total mass of the reaction product exiting thereactor.

The reaction product stream can comprise about 10% to about 60% by masscarbon dioxide, based on the total mass of the reaction product exitingthe reactor.

The primary heat exchanger can be a transfer line exchanger (TLE).

The reaction product stream exiting the primary heat exchanger can be ata temperature of about 200° C. to about 400° C.

Removing water and optionally any further condensates in the reactionproduct stream can comprise passing the reaction product stream througha condensing unit.

The reaction product stream can be cooled in the condensing unit toabout ambient temperature.

Heating at least a portion of the carbon dioxide separated from thereaction product stream using the heat withdrawn from the reactionproduct stream can comprise passing the carbon dioxide through asecondary heat exchanger against a circulating stream that is heated inthe primary heat exchanger using the heat withdrawn from the reactionproduct stream.

Recycling the stream of heated carbon dioxide back into the reactor cancomprise one or more of the following: injecting the stream of heatedcarbon dioxide directly into the reactor; injecting the stream of heatedcarbon dioxide into a carbon dioxide source; injecting the stream ofheated carbon dioxide into a line delivering carbon dioxide from acarbon dioxide source to the reactor; injecting the stream of heatedcarbon dioxide into an ethane source; injecting the stream of heatedcarbon dioxide into a line delivering ethane from an ethane source tothe reactor.

The at least a portion of the stream of heated carbon dioxide can bepassed through a line heater configured for transfer of heat from thestream of heated carbon dioxide to one or more streams being passed intothe reactor.

A portion of the heat withdrawn from the reaction product stream in theprimary heat exchanger can be used for heating one or more of thefollowing: the reactor; a carbon dioxide source; a carbon dioxide linedelivering carbon dioxide from a carbon dioxide source to the reactor;an ethane source; an ethane line delivering ethane from an ethane sourceto the reactor.

A portion of the heat withdrawn from the reaction product stream in theprimary heat exchanger can be used for heating one or both of apressurized steam stream and a pressurized CO₂ stream for use in powergeneration in a closed loop or semi-open loop power production systemwherein a working stream is repeatedly compressed and expanded for powerproduction.

A portion of the heat withdrawn from the reaction product stream in theprimary heat exchanger can be used for heating a steam stream that isinjected into the reactor.

Further processing the upgraded ethylene stream can comprise one or moreof the following steps: passing the upgraded ethylene stream through anadsorber to adsorb any water in the upgraded ethylene stream; passingthe upgraded ethylene stream through a refrigeration unit to cool theupgraded ethylene stream to a temperature of less than −50° C.; passingthe upgraded ethylene stream through a de-methanizer unit; passing theupgraded ethylene stream through a de-ethanizer unit; passing a mixtureof ethane and ethylene from the de-ethanizer into a C2 splitter unit.

The method can comprise injecting steam into the reactor.

In one or more embodiments, the present disclosure can related tosystems for chemical production from ethane. In example embodiments,such systems can comprise: a catalytic reactor configured for reactingethane with carbon dioxide at a temperature of about 450° C. or greaterto form a reaction product stream including at least ethylene and carbondioxide; an ethane line configured for delivery of ethane into thecatalytic reactor; a carbon dioxide line configured for delivery ofcarbon dioxide into the catalytic reactor; a primary heat exchangerconfigured to receive the reaction product stream from the catalyticreactor and withdraw heat therefrom; a gas-liquid separation unitconfigured for removal of water and optionally other condensates fromthe reaction product stream; a compressor configured for compressing thereaction product to a pressure of at least 20 bar; a carbon dioxideseparation unit configured for receiving the reaction product streamdownstream of the primary heat exchanger and for separating at least aportion of the carbon dioxide from the reaction product stream toprovide an upgraded ethylene stream; a line configured for delivering atleast a portion of the carbon dioxide separated from the reactionproduct stream in the carbon dioxide separation unit to the reactorwhile being heated with at least a portion of the heat withdrawn fromthe reaction product stream in the primary heat exchanger. In furtherembodiments, the systems can be characterized by one or more of thefollowing statements, which statements can be combined in any order ornumber.

The system can comprise a secondary heat exchanger, wherein the lineconfigured for delivering at least a portion of the carbon dioxideseparated from the reaction product stream in the carbon dioxideseparation unit to the reactor can pass through the secondary heatexchanger for heating against a line passing a heated circulating streamfrom the primary heat exchanger.

The system can comprise a line heater configured for heating one or bothof the ethane line and the carbon dioxide line.

The system can comprise one or more lines configured for delivering aheated stream from the primary heat exchanger to the line heater.

The system can comprise one or more lines configured for delivering aheated stream from the primary heat exchanger for transfer of heat toone or more of the following: the reactor; a carbon dioxide source; anethane source.

The line configured for delivering at least a portion of the carbondioxide separated from the reaction product stream in the carbon dioxideseparation unit to the reactor can be specifically configured fordelivering at least a portion of the carbon dioxide into one or both ofthe carbon dioxide line and the ethane line.

The system can comprise a thermal energy source configured for heatingthe reactor.

The thermal energy source can comprise one or more of the following: aconcentrated solar energy heater; a combustion heater; a geothermalheater; an external industrial heat source.

The can comprise one or more of the following components configured forreceiving the upgraded ethylene stream: a compressor configured forcompressing the upgraded ethylene stream to a pressure of at least 10bar; an adsorber configured for adsorbing any water in the upgradedethylene stream; a refrigeration unit configured to cool the upgradedethylene stream to a temperature of less than −50° C.; a de-methanizerunit; a de-ethanizer unit; a C2 splitter unit.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a flow diagram showing an example embodiment of a processwherein ethane is subjected to oxidative dehydrogenation utilizingcarbon dioxide as a soft oxidant.

FIG. 2 is a flow diagram showing another example embodiment of a processwherein ethane is subjected to oxidative dehydrogenation utilizingcarbon dioxide as a soft oxidant.

FIG. 3 is a flow diagram showing yet another example embodiment of aprocess wherein ethane is subjected to oxidative dehydrogenationutilizing carbon dioxide as a soft oxidant.

DETAILED DESCRIPTION

The present subject matter will now be described more fully hereinafterwith reference to exemplary embodiments thereof. These exemplaryembodiments are described so that this disclosure will be thorough andcomplete, and will fully convey the scope of the subject matter to thoseskilled in the art. Indeed, the subject matter can be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will satisfy applicable legal requirements. As usedin the specification, and in the appended claims, the singular forms“a”, “an”, “the”, include plural referents unless the context clearlydictates otherwise.

The present disclosure relates to methods for chemical production fromethane. The disclosed methods utilize oxidative dehydrogenation of theethane by carbon dioxide cracking. The reaction is preferably catalytic,and various catalysts may be used. For example, in some embodiments, asolid particle heater may be utilized as the reactor wherein particlescoated with a mixed transition metal catalyst (or like material) can beheated (e.g., using concentrated solar power) to provide a hybridthermal catalyst. Such hybrid thermal catalyst can be useful to drive areaction for oxidative dehydrogenation of ethane to ethylene usingcarbon dioxide as a soft oxidant as shown below.C₂H₆+CO₂+heat→C₂H₄+H₂O+COThe produced CO may be separated and fully oxidized to drive a turbine.Alternatively, a water gas shift reaction (WGSR) may be used with theproduced H₂O and CO to produce H₂ gas. This would provide a net reactionas shown below.C₂H₆+heat→C₂H₄+H₂In such methods utilizing particle flow systems, the catalyst particlesmay be subjected to regeneration/cleaning, which can reduceinterruptions in the process. Moreover, the process may be applied to avariety of industrial reactions by utilizing varying catalytic coatingson the particles. The catalyst may be provided as a coating on a varietyof elements. For example, in some embodiments, the catalyst may becoated onto the inner surface of one or more pipes or tubes such thatthe catalytic reactions may occur as the ethane and carbon dioxide flowthrough the pipes and make contact with the catalyst.

In one or more embodiments, a method for carbon dioxide cracking ofethane can be carried as generally described in the process diagramshown in FIG. 1. In particular, ethane from ethane source 101 isprovided through line 103, and carbon dioxide from carbon dioxide source102 is provided through line 104 into a reactor 110. The ethane and thecarbon dioxide may be added separately to the reactor 110 or may becombined prior to passage into the reactor. In some embodiments, theethane and/or the carbon dioxide in line 103 and line 104, respectively,may be passed through an optional line heater 105, which particularlymay be configured for transfer of heat to one or more streams beingpassed to the reactor. The reactor 110 can be any suitable type ofreactor, such as a fixed bed reactor catalytic reactor or a fluidizedbed catalytic reactor containing a suitable catalyst. Additionalcatalyst may be added to the reactor 110 as needed. Thermal energy issupplied for the reaction from one or a combination of sources. Asfurther described herein, recuperative heating may particularly beutilized. In addition, a thermal energy source 112 may supply thethermal energy to any one or a combination of the following: directly tothe reactor 110 through line 112 a; to the line heater 105 through line112 b; to the carbon dioxide line 104 through line 112 c; to the carbondioxide source 102 through line 112 d; to the ethane source 101 throughline 112 e; to the ethane line 103 through line 112 f. The thermalenergy source 112 can be one, or a combination of the following sourcesof a thermal energy source; a concentrated solar energy heat source; asource for heat of combustion; an external industrial heat source.

Within the reactor 110, oxidative dehydrogenation (ODH) of ethane isperformed to yield at least ethylene (and/or other suitable olefins),carbon monoxide, hydrogen, and water. As further described below,further chemical products likewise can be present in the reactionproduct stream and can be handled according to the present embodiment bycombination of further steps as otherwise described herein. Returning toFIG. 1, the reaction product stream exits the reactor 110 in line 115and is passed to an ethylene separation unit 120 from which ethylene iswithdrawn in line 121. The remaining reaction product, including carbonmonoxide, hydrogen, and water, exits in line 122.

The carbon monoxide, hydrogen, and water mixture in line 122 can beseparated into two streams from separator 125. A mole (X) of the carbonmonoxide, hydrogen, and water mixture is bled off in line 130 and cooledin condenser 135 to separate out water in line 136 via condensation andprovide purified CO/H₂ in line 137. A mole fraction (1−X) of the carbonmonoxide, hydrogen, and water mixture is bled off in line 140 andundergoes a water gas shift reaction in a WGS reactor 145 to provide amixture of carbon dioxide and hydrogen gas in line 147. The mixture ofcarbon dioxide and hydrogen is separated in separator 155 to provide astream of recycled carbon dioxide in line 157, which can be recycledinto one or more of the following: directly into the reactor 110; intothe carbon dioxide source 102; into the carbon dioxide line 104; intothe line heater 105; into the ethane source 101; into the ethane line103. The carbon dioxide in the line 157 may be heated utilizing wasteheat taken from the reaction product in line 115, such as using anoptional recuperator heat exchanger 162. The separator 155 utilized toseparate hydrogen gas from the carbon dioxide can utilize any one ormore of the following separation methods: pressure swing adsorption(PSA); membrane separation; cryogenic separation. The resulting hydrogenstream leaving in line 159 can be compressed (e.g., to a pressure of atleast 20 bar, at least 30 bar, or at least 50 bar, such as from about 20bar to about 150 bar, about 30 bar to about 125 bar, or about 50 bar toabout 100 bar, specifically to about 74 bar) for providing as acommodity or for use in power production. In some embodiments, at leasta portion of the hydrogen in line 159 may be passed through line 160 tounion 165 to be combined with at least a portion of the carbon monoxidefrom line 137 to provide a stream of combined carbon monoxide andhydrogen gas in line 166. The stream of combined carbon monoxide andhydrogen gas in line 166 can be exported as a synthesis gas product tobe used in power production. Likewise, at least a portion of thesynthesis gas exported from line 166 may be combusted for heatproduction in thermal energy source 112. If desired, at least a portionof combined carbon monoxide and hydrogen gas in line 166 can be providedthrough line 167 into synthesis unit 170 for production of furtherchemicals. For example, the synthesis unit 170 may comprise a methanolsynthesis unit, and the mixture of combined carbon monoxide and hydrogengas can be utilized for methanol synthesis. In such instances, theproduced methanol in line 171 can be subjected to a dehydration reactionproducing a separate stream of ethylene and water.

A further example embodiment of the present method is illustrated inFIG. 2. As seen therein, ethane from ethane source 201 is providedthrough line 203, and carbon dioxide from carbon dioxide source 202 isprovided through line 204 into a reactor 210. The ethane and the carbondioxide may be added separately to the reactor 210 or may be combinedprior to passage into the reactor. In some embodiments, the ethaneand/or the carbon dioxide in line 203 and line 204, respectively, may bepassed through an optional line heater 205, which particularly may beconfigured for transfer of heat to one or more streams being passed tothe reactor. The reactor 210 again can be any suitable type of reactor;however, it preferably is a catalytic reactor containing a suitablecatalyst (which may be replenished as needed through addition of make-upcatalyst). Thermal energy is supplied for the reaction from one or acombination of sources, as already described. Specifically, a thermalenergy source 212 may supply the thermal energy to any one or acombination of the following: directly to the reactor 210 through line212 a; to the line heater 205 through line 212 b; to the carbon dioxideline 204 through line 212 c; to the carbon dioxide source 202 throughline 212 d; to the ethane source 201 through line 212 e; to the ethaneline 203 through line 212 f.

Within the reactor 210, oxidative dehydrogenation (ODH) of ethane isperformed to yield at least ethylene (and/or other suitable olefins),carbon monoxide, hydrogen, and water. The reaction product stream exitsthe reactor 210 in line 215 and is passed to WGS reactor 245 to providea mixed stream of carbon monoxide, hydrogen, carbon dioxide, andethylene in line 247. The molar fraction of carbon monoxide and hydrogenprovided in line 247 can be tuned to various ratios dependent upon theextent of the reaction in the WGS reactor 245. The mixed stream ofcarbon monoxide, hydrogen, carbon dioxide, and ethylene is passedthrough separator 255 to be separated into three streams. A first streamformed of recycled carbon dioxide passes through stream 257 to berecycled into one or more of the following: directly into the reactor210; into the carbon dioxide source 202; into the carbon dioxide line204; into the line heater 205; into the ethane source 201; into theethane line 203. The carbon dioxide in the line 257 may be heatedutilizing waste heat taken from the reaction product in line 215, suchas using an optional recuperator heat exchanger 262. A second streamformed of ethylene leaves in line 221. A third stream comprising amixture of carbon monoxide, hydrogen, and carbon dioxide leaves in line267 and can be processed for further chemical production. For example,at least a portion of the mixture of carbon monoxide, hydrogen, andcarbon dioxide can be passed through line 268 into a methanol synthesisunit 270 to produce methanol in line 271, which can be subjected to adehydration reaction producing a separate stream of ethylene and water.

In one or more embodiments, the presently disclosed methods can beparticularly useful in that the amount of carbon dioxide utilized in thecracking process can be beneficially increased beyond the requiredamount so that the reaction stream can include an excess of carbondioxide. This can include providing ethane and carbon dioxide into thereactor at a molar ratio so that the amount of provided carbon dioxideis in excess of the stoichiometrically required amount for completereaction with the ethane. The molar excess of carbon dioxide can besufficient so that the reaction product exiting the reactor can compriseat least 5% by mass, at least 10% by mass, at least 20% by mass, atleast 25% by mass, at least 30% by mass, or at least 40% by mass carbondioxide, particularly up to a maximum of about 80% by mass carbondioxide, based on the total mass of the reaction product exiting thereactor. In preferred embodiments, the reaction product exiting thereactor can comprise about 5% to about 70%, about 10% to about 60%, orabout 20% to about 50% by mass carbon dioxide, based on the total massof the reaction product exiting the reactor. The presence of excesscarbon dioxide is beneficial for multiple reasons. For example, theprovision of excess carbon dioxide can ensure that maximum ethaneconversion occurs in the reactor. It further can provide a large mass ofrecyclable material that can reduce the amount of make-up carbon dioxidethat may be replenished into the reactor. It still further can provide alarge amount of heat that can be recuperated to reduce the amount ofenergy that must be expended for heating in the reactor.

The advantages of utilizing an excess of carbon dioxide in the reactionis further illustrated in relation to FIG. 3. As seen therein, ethanefrom ethane source 301 is provided through line 303, and carbon dioxidefrom carbon dioxide source 302 is provided through line 304 into areactor 310. The ethane and the carbon dioxide may be added separatelyto the reactor 310 or may be combined prior to passage into the reactor.In some embodiments, the ethane and/or the carbon dioxide in line 303and line 304, respectively, may be passed through an optional lineheater 305, which particularly may be configured for transfer of heat toone or more streams being passed to the reactor. The reactor 310 againcan be any suitable type of reactor; however, it preferably is acatalytic reactor containing a suitable catalyst (which may bereplenished as needed through addition of make-up catalyst). Thermalenergy is supplied for the reaction from one or a combination ofsources, as already described. Specifically, a thermal energy source 312may supply the thermal energy to any one or a combination of thefollowing: directly to the reactor 310 through line 312 a; to the lineheater 305 through line 312 b; to the carbon dioxide line 304 throughline 312 c; to the carbon dioxide source 302 through line 312 d; to theethane source 301 through line 312 e; to the ethane line 303 throughline 312 f. In a particular embodiment, both of the ethane in line 303and the carbon dioxide in line 304 are preheated in the line heater 305prior to being sent to the reactor 310. Such heating alone can besufficient to provide the desired reaction temperature within thereactor 301; however, further heating can be provided directly to thereactor. In some embodiments, a steam stream may be provided in line 312a to deliver thermal energy from the thermal energy source 312.Alternatively, a steam stream may be provided in addition to the thermalenergy from the thermal energy source.

The reaction within the reactor is preferably carried out at atemperature of at least 450° C., at least 475° C., or at least 500° C.,such as up to a maximum temperature of about 1000° C. In preferredembodiments, the temperature within the reactor 310 for reaction tooccur is in the range of about 450° C. to about 1000° C., about 500° C.to about 800° C., or about 550° C. to about 700° C. Such temperaturescan further apply to other embodiments described herein. The reaction ofethane with carbon dioxide in the reactor produces a reaction productstream comprising at least ethylene, carbon monoxide, water, and carbondioxide, but also can include unreacted ethane, hydrogen, methane, andtraces of heavier hydrocarbons. The mixture of reaction produces exitsthe reactor 310 in line 315 and is passed into a heat exchanger 362. Theheat exchanger 362 can be referenced as a primary heat exchanger 362 forsimplicity of identification. In an example embodiment, the heatexchanger 362 can be a transfer line exchanger (TLE). Passage throughthe TLE rapidly cools the reaction product down to a temperature ofabout 200° C. to about 400° C., which is beneficial to substantiallyprevent further occurrence of side reactions and thus reduce oreliminate production of undesired by-products. Waste heat (Q) withdrawnfrom the reaction product stream can be utilized for multiple purposes.For example, the waste heat may be utilized to preheat the reactor feedstreams. As such, heat provided through one or more of streams 312 athrough 312 f may be heat provided from heat exchanger 362. In thismanner, heat withdrawn from the reaction product stream may be used toheat the ethane stream and/or the carbon dioxide stream. Likewise, heatwithdrawn from the reaction product stream may be used to provide heatdirectly to the reactor 310. As illustrated in FIG. 3, a first heatquantity (Q1) is withdrawn from the heat exchanger 362 to be used toprovide heat to any of the reactor 310, the ethane source 301, theethane line 303, the carbon dioxide source 302, and the carbon dioxideline 304. In further embodiments, as illustrated in FIG. 3, waste heat(Q2) from the heat exchanger 362 can be used to heat a high pressuresteam stream and/or a high pressure CO₂ stream for use in powergeneration in a closed loop or semi-open loop power production systemwherein a working stream is repeatedly compressed and expanded for powerproduction. As such, the presently disclosed methods can be reliablycombined with any systems and methods that are known for powerproduction, and particularly with systems and methods that are known toproduce CO₂. For example, U.S. Pat. Nos. 8,596,075, 8,776,532,8,959,887, 8,986,002, 9,068,743, 9,416,728, 9,546,814, 10,018,115, andU.S. Pub. No. 2012/0067054, the disclosures of which are incorporatedherein by reference, all describe system and methods that may becombined with the presently disclosed methods. Such systems and methodscan be a reliable source of CO₂ for use in the chemical conversionprocess. Likewise, waste heat from heat exchanger 362 may be used toprovide added heating in such systems and methods.

The reaction product stream, after being cooled in the heat exchanger362, can be passed through line 317 to a gas-liquid separator 335, suchas a water separation tower or other condensing unit in order to furthercool the reaction product stream to approximately ambient temperatureand remove water and other condensates by use of a quench water orquench oil. As shown in FIG. 3, water and any entrained condensates arewithdrawn through stream 336.

The reaction product stream can be subject to a variety of process stepsby passage through one or more system units in order to upgrade theethylene concentration in the reaction product stream. An upgradedethylene stream thus can be defined as a stream comprising a higherweight percentage of ethylene than the stream from which it was derived.This can be achieved through, for example, removal of one or more othercomponents from the reaction product stream, such as carbon dioxide,hydrogen sulfide, and other acid gases. In some embodiments, an enrichedor upgraded ethylene stream may be referred to as a cleaned reactionproduct stream since it still contains at least a portion of thereaction products (e.g., ethylene) and has been cleaned of at least aportion of the non-ethylene constituents (e.g., carbon dioxide, water,etc.).

The reaction product stream is preferably compressed to enhance theseparation of further components of the reaction product stream, such asthrough use of absorbents, adsorbents, and/or membrane separators. Thehigh pressure operation of downstream units, such as the carbon dioxideseparator 355, can also be useful to reduce the equipment size and thusthe required capital cost.

The quenched reaction product stream in line 337 can be compressed to apressure of at least 20 bar, at least 25 bar, or at least 30 bar (e.g.,with a maximum of about 100 bar), and preferably is compressed to apressure of about 10 bar to about 100 bar, about 20 bar to about 90 bar,or about 30 bar to about 80 bar. As illustrated, in FIG. 3, thecompression is carried out using a multi-stage intercooled centrifugalcompressor 361; however, any alternative compressor suitable to providethe necessary compression may be used. Optionally, a caustic soda washcan be applied at the exit of each compression stage to remove traces ofacid gas from the process stream.

The quenched and compressed reaction product stream in line 359 can bedirected to a carbon dioxide separator 355 wherein carbon dioxide isseparated from the reaction product stream to form a firstethylene-enriched stream in line 364 and a recycled carbon dioxidestream in line 357. The first ethylene-enriched stream in line 364 canbe considered to be an upgraded ethylene stream because the weightpercentage of ethylene in the stream in line 364 is greater than theweight percentage of ethylene in the quenched reaction product stream inline 337 and/or the compressed reaction product stream in line 359. Therecycled carbon dioxide in stream 357 can be heated using waste heat(Q3) from the heat exchanger 362. It is understood that in any or allcases wherein waste heat is utilized, the stream being heated may passthrough the heat exchanger 362, or a secondary circulating heating fluidmay be circulated through the heat exchanger for heat transfer to thefurther stream being heated. As such, one or more additional heatexchangers may be utilized to transfer heat from a circulating fluid tothe stream in a given line without commingling of the streams. Asillustrated in FIG. 3, the recycled carbon dioxide in stream 357 can beheated with waste heat (Q3) by passage through the secondary heatexchanger 363. In an example embodiment, a circulating fluid may becirculated through the primary heat exchanger 362 and the secondary heatexchanger 363 so that the carbon dioxide in line 357 is heated using theheat withdrawn from the reaction product stream in the primary heatexchanger 362. Although not shown in FIG. 3, is understood that the line(Q3) would pass from the secondary heat exchanger 363 and back into theprimary heat exchanger 362 for further withdrawal of heat from thereaction product stream. The recycled carbon dioxide in stream 357 thatis heated with waste heat (Q3) may be combined with any one or more ofthe following to provide heating: the reactor 310; the carbon dioxidesource 302; the carbon dioxide line 304; the line heater 305; the ethanesource 301; the ethane line 303. In this manner, the recycled carbondioxide can be recycled back for the dehydrogenation reaction with freshethane and reduce the amount of added carbon dioxide that must be addedto the reaction.

The carbon dioxide separator 355 can be configured to utilize a varietyof unit operations such as an absorption tower, an adsorption bed, amembrane-based separator, a refrigeration process, or any combinationthereof. Separation of the carbon dioxide is preferred to be carriedprior to downstream separation of hydrocarbon and other species withinthe reaction product stream as such separation typically involvesrefrigeration and cooling of process gas to temperatures that exceedsthe triple point of carbon dioxide, and cooling the carbon dioxide tosuch temperature can cause sublimation and formation of solid carbondioxide within the piping and equipment.

Although the carbon dioxide separator 355 is illustrated as beingdownstream from the compressor 361, in some embodiments, carbon dioxideseparation may be carried out between compression states. As such, thereaction product stream in line 337 may first pass to a first stagecompressor 361 a, then to a carbon dioxide separator 355, and then to asecond stage compressor 361 b. The carbon dioxide separator 355, forexample, may be positioned between an intercooler 361 c and the secondstage compressor 361 b. In further embodiments, the carbon dioxideseparator 355 may be configured to be fully upstream from the compressor361. As such, substantially no compression may be carried out prior tocarbon dioxide separation. In further embodiments, however, asupplemental compressor may be provided downstream from the gas-liquidseparator 335 to compress the reaction product stream to a firstpressure (e.g., up to about 15 bar, such as about 5 bar to about 15 bar)at which carbon dioxide separation is carried out, and the reactionproduct stream exiting the carbon dioxide separator may be passed to thecompressor 361 to be compressed to a second, greater pressure.

The compressed, first ethylene-enriched stream exits the carbon dioxideseparator 355 in line 364 and is passed to an adsorber 375, which cancomprise an adsorbent bed of appropriate material (such as molecularsieves). The material utilized in the adsorber 375 is preferablyconfigured to remove traces of moisture which could otherwise freeze andform ice in the downstream piping and equipment that are operated belowthe freezing point of water.

The dried and pressurized first ethylene-enriched stream exiting theadsorber in line 376 is then fed into a refrigeration unit 377 where itis cooled to a temperature that is less than −50° C., less than −100°C., or less than −150° C., preferably being cooled to a temperaturerange of about −50° C. to about −200° C., about −100° C. to about −190°C., or about −150° C. to about −180° C., particularly to a temperatureof about −165° C. The dried and pressurized first ethylene-enrichedstream is preferably at a temperature and pressure such that hydrogenand carbon monoxide present in the stream remains in the vapor stagewhile other constituents of first ethylene-enriched stream will liquefyand can be separated therefrom. As such, the refrigeration unit 377 cancomprise a phase separator.

Exiting the refrigeration unit in stream 340 is a mixture of carbonmonoxide and hydrogen which can be used in chemical production asalready described above. For example, the mixture of carbon monoxide andhydrogen in stream 340 can be passed to a WGS reactor 345 to provide amixed stream of carbon monoxide and hydrogen, which can be used indownstream chemical production, such as methanol and/or Fischer-Tropsch(FT) synthesis. The ratio of carbon monoxide and hydrogen can beoptionally adjusted in a water-gas shift step to meet the chemicalproduction requirement.

A second ethylene-enriched stream exits the refrigeration unit 377 inline 379 and is fed to a de-methanizer unit 380 to separate any methanetherefrom. Further to the above discussion, the second ethylene-enrichedstream in line 379 can be considered to be an upgraded ethylene streamsince it comprises a greater weight percentage of ethylene when comparedto the stream immediately upstream in line 376 that is passed throughthe refrigeration unit 377. A methane-rich stream exits thede-methanizer unit 380 in line 381. The methane-rich stream may beexported as a commodity. In some embodiments, at least a portion of themethane may be withdrawn in line 382 to be utilized in the reactor 310to provide reaction heating and/or to be utilized in thermal energysource 312 to provide combustion heating.

A third ethylene-enriched stream (which likewise can be considered to bean upgraded ethylene stream) also exits the de-methanizer unit 380 inline 385 and is fed to a de-ethanizer column 387. A bottom productcomprised of C3 and greater hydrocarbons is bled off in line 389. Insome embodiments, methane and other light gases from the top section ofthe de-methanizer column unit can be used as a supplementary fuel forsue in the reactor 310 and/or the thermal energy source 312. In furtherembodiments, uncoverted ethane from the C2 splitter can be used as asupplementary fuel for sue in the reactor 310 and/or the thermal energysource 312.

A fourth-ethylene enriched stream (comprising predominately ethylene andethane) is passed through line 391 into a C2-splitter column 392 tofurther fractionate the stream into its main constituents, ethylene andethane. An overhead ethane stream in line 393 from the C2-splittercolumn 392 is recycled back to the dehydrogenation reactor 310. A streamof purified ethylene leaves the bottom of the C2-splitter column 392 inline 395. The separation and purification of heavier hydrocarbons in thestream from the bottom of the de-ethanizer unit 387 can be carried outin any appropriate combinations of de-propanizer/C3-splitter,debutanizer/C4-splitter and so on.

As seen from the foregoing, the present disclosure provides asustainable and environmentally friendly method for the production ofethylene, H₂, and methanol, which are the three most fundamentalbuilding blocks for the chemical industry globally. Ethylene is the mostproduced organic compound on earth, and it is known to be used innumerous products. The presently disclosed methods can enable industryto produce ethylene using less energy, while producing H₂, methanol, andeven further chemical products as well. Moreover, the disclosed methodsalso consume CO₂ by essentially “fixing” it into compounds whoseultimate use will not re-emit that CO₂.

Many modifications and other embodiments of the presently disclosedsubject matter will come to mind to one skilled in the art to which thissubject matter pertains having the benefit of the teachings presented inthe foregoing descriptions and the associated drawings. Therefore, it isto be understood that the present disclosure is not to be limited to thespecific embodiments described herein and that modifications and otherembodiments are intended to be included within the scope of the appendedclaims. Although specific terms are employed herein, they are used in ageneric and descriptive sense only and not for purposes of limitation.

The invention claimed is:
 1. A method for chemical production, themethod comprising: providing one or more hydrocarbons and carbon dioxideinto a reactor at a molar ratio so that the amount of provided carbondioxide is in excess of the stoichiometrically required amount forcomplete reaction with the one or more hydrocarbons; reacting the one ormore hydrocarbons with the carbon dioxide in the reactor in the presenceof a catalyst to form a reaction product stream comprising one or moreolefins, water, and carbon dioxide; passing the reaction product streamthrough a primary heat exchanger to withdraw heat therefrom; removingwater and optionally any further condensates present in the reactionproduct stream; compressing the reaction product stream to a pressure ofat least 20 bar; separating carbon dioxide from the reaction productstream in a separation unit to provide an upgraded stream comprising theone or more olefins.
 2. The method claim 1, further comprising: heatingat least a portion of the carbon dioxide separated from the reactionproduct stream using the heat withdrawn from the reaction product streamto form a stream of heated carbon dioxide; and recycling the stream ofheated carbon dioxide back into the reactor.
 3. The method of claim 2,wherein recycling the stream of heated carbon dioxide back into thereactor comprises one or more of the following: injecting the stream ofheated carbon dioxide directly into the reactor; injecting the stream ofheated carbon dioxide into a carbon dioxide source; injecting the streamof heated carbon dioxide into a line delivering carbon dioxide from acarbon dioxide source to the reactor; injecting the stream of heatedcarbon dioxide into a source of the one or more hydrocarbons; injectingthe stream of heated carbon dioxide into a line delivering the one ormore hydrocarbons from a source of the one or more hydrocarbons to thereactor.
 4. The method of claim 2, wherein the at least a portion of thestream of heated carbon dioxide is passed through a line heaterconfigured for transfer of heat from the stream of heated carbon dioxideto one or more streams being passed into the reactor.
 5. The method ofclaim 1, wherein the reactor is a fixed bed reactor catalytic reactor ora fluidized bed catalytic reactor.
 6. The method of claim 1, wherein thereaction product stream is at a temperature of about 500° C. to about800° C.
 7. The method of claim 1, wherein the reaction product streamcomprises about 10% to about 60% by mass carbon dioxide, based on thetotal mass of the reaction product exiting the reactor.
 8. The method ofclaim 1, wherein the primary heat exchanger is a transfer line exchanger(TLE).
 9. The method of claim 1, wherein the reaction product streamexiting the primary heat exchanger is at a temperature of about 200° C.to about 400° C.
 10. The method of claim 1, wherein removing water andoptionally any further condensates present in the reaction productcomprises passing the reaction product stream through a condensing unit.11. The method of claim 1, wherein heating at least a portion of thecarbon dioxide separated from the reaction product stream using the heatwithdrawn from the reaction product stream comprises passing the carbondioxide through a secondary heat exchanger against a circulating streamthat is heated in the primary heat exchanger using the heat withdrawnfrom the reaction product stream.
 12. The method of claim 1, wherein aportion of the heat withdrawn from the reaction product stream in theprimary heat exchanger is used for heating one or more of the following:the reactor; a carbon dioxide source; a carbon dioxide line deliveringcarbon dioxide from a carbon dioxide source to the reactor; a source ofthe one or more hydrocarbons; a line delivering the one or morehydrocarbons from a source of the one or more hydrocarbons to thereactor.
 13. The method of claim 1, wherein a portion of the heatwithdrawn from the reaction product stream in the primary heat exchangeris used for heating one or both of a pressurized steam stream and apressurized CO₂ stream for use in power generation in a closed loop orsemi-open loop power production system wherein a working stream isrepeatedly compressed and expanded for power production.
 14. The methodof claim 1, wherein a portion of the heat withdrawn from the reactionproduct stream in the primary heat exchanger is used for heating a steamstream that is injected into the reactor.
 15. The method of claim 1,further comprising processing the upgraded stream comprising the one ormore olefins to provide at least one chemical product, said processingcomprising one or more of the following steps: passing the upgradedstream comprising the one or more olefins through an adsorber to adsorbany water in the upgraded stream comprising the one or more olefins;passing the upgraded stream comprising the one or more olefins through arefrigeration unit to cool the upgraded stream comprising the one ormore olefins to a temperature of less than −50° C.; passing the upgradedstream comprising the one or more olefins through a de-methanizer unit;passing the upgraded stream comprising the one or more olefins through ade-ethanizer unit.
 16. The method of claim 1, comprising injecting steaminto the reactor.
 17. The method of claim 1, wherein the one or morehydrocarbons comprises one or more of ethane, propane, and butane.
 18. Asystem for chemical production, the system comprising: a catalyticreactor configured for reacting one or more hydrocarbons with carbondioxide at a temperature of about 450° C. or greater to form a reactionproduct stream including at least carbon dioxide and one or moreolefins; a line configured for delivery of the one or more hydrocarbonsinto the catalytic reactor; a line configured for delivery of carbondioxide into the catalytic reactor; a primary heat exchanger configuredto receive the reaction product stream from the catalytic reactor andwithdraw heat therefrom; a gas-liquid separation unit configured forremoval of water and optionally other condensates from the reactionproduct stream; a compressor configured for compressing the reactionproduct stream to a pressure of at least 20 bars; a carbon dioxideseparation unit configured for receiving the reaction product streamafter at least one stage of compression and for separating at least aportion of the carbon dioxide from the reaction product stream toprovide an upgraded stream comprising the one or more olefins; and aline configured for delivering at least a portion of the carbon dioxideseparated from the reaction product stream in the carbon dioxideseparation unit to the reactor while being heated with at least aportion of the heat withdrawn from the reaction product stream in theprimary heat exchanger.
 19. The system of claim 18, comprising asecondary heat exchanger, wherein the line configured for delivering atleast a portion of the carbon dioxide separated from the reactionproduct stream in the carbon dioxide separation unit to the reactorpasses through the secondary heat exchanger for heating against a linepassing a heated circulating stream from the primary heat exchanger. 20.The system of claim 18, comprising a line heater configured for heatingone or both of the line configured for delivery of the one or morehydrocarbons and the line configured for delivery of the carbon dioxide,and comprising one or more lines configured for delivering a heatedstream from the primary heat exchanger to the line heater.
 21. Thesystem of claim 18, comprising one or more lines configured fordelivering a heated stream from the primary heat exchanger for transferof heat to one or more of the following: the reactor; a carbon dioxidesource; an ethane source.
 22. The system of claim 18, comprising athermal energy source configured for heating the reactor, wherein thethermal energy source comprises one or more of the following: aconcentrated solar energy heater; a combustion heater; an externalindustrial heat source.